The invention relates to a method of applying a fluid to a surface, the pressurised fluid being applied from a container to the surface through a hollow needle. The invention also relates to an arrangement for carrying out said method.
Such a method is known from DE-A-37 28 054.
A frequently occurring problem with this known method is clogging of the hollow needle. When the fluid is a solder paste clogging is caused particularly by segregation of the solder paste near the transition from the container to the needle. The flux then separates from the soldering powder globules because the specific mass of the soldering powder globules is higher than that of the flux. This results in solder powder globules accumulating in the lower part of the container and thereby obstructing the entrance to the needle. When the paste is subjected to pressure impulses in order to apply the paste, the solder powder globules are compressed additionally, which promotes the clogging process. When the fluid is an adhesive, clogging is caused by premature curing of the adhesive, particularly because pressure pulses cause a rise in temperature. The pressure to which the fluid is subjected may result merely from the hydrostatic pressure of the fluid itself or, in addition, an external pressure produced by separate pressure means.